Goldschmidt 2012 Conference Abstracts
The Major Element Composition of
Earth’s Core
JAMES BADRO1*, JOHN BRODHOLT2, ALEXANDER COTE1,2
1IPGP,
2UCL,
Paris, France, badro@ipgp.fr (* presenting author)
London, UK, j.brodholt@ucl.ac.uk
Earth’s core formed as a results of a major chemical
differentiation event; the melting of accretionary building blocks
(meteorites, planetesimals, protoplanets) leads to a separation of the
metal from the silicate, ensued by a gravitationally-driven
segregation of a dense metal-rich core at the centre of the planet, with
the lighter buoyant silicates remaining on top to form the mantle and
crust. The bulk composition of the core depends on the path and
conditions (pressure, temperature, redox) at which core formation
took place; the process also leaves an imprint on the residual bulk
silicate Earth, a record that is observable in present-day mantle rocks.
Constraining experimental and theoretical data with geophysical
(core density and velocity profiles) observations provides a robust
way to estimate the present day composition of the core, as well as
the conditions under which it formed.
We will present results obtained from ab initio molecular
dynamics calculations to estimate outer-core density and seismic
velocity, and combine it with mineral physics on the inner core to
define a range of possible compositions of the core that satisfies the
observations. We will interpret these results and propose a consistent
compositional model, and formulate plausible scenarios for core
formation.
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